Electric heater



June 25,` 1929' E. cRooKER Er AL ELECTRIC HEATER Filed Feb. 6, 1925 EN :A v mmm H E. .M H /S ,A mmww. Hf

Patented June 25, 1929.

UNITED STATES 1,718,412 PATENT OFFICE.

EDWIN R. CROOXER AND HARRY C. NEWMAN, OF LOS ANGELES, CALIFORNIA; SAID NEWMAN ASSIGNOR TO SAID CROOKER.

ELECTRIC HEATER.

Application led February 6, 1925. Serial No. 7,235.

Our present invention is an electric heater which is suitable for various uses, and which is not liable easily to get out of order, although it is adapted to be manufactured and sold at comparatively small cost.

It is an object of this invention to provide an electric heater which, although it may be rigid, is sufficiently fiat and thin to be suitable for, for example, hospital uses, such as the Warming of a bed or of parts of the human body; and a preferred embodiment of this invention may comprise a sheet metal casing adapted to receive and to protect all essential parts thereof, retaining the same in their intended relationships, this container being suitable, upon the removal of an optional cloth cover therefrom, for insei-tion, in the customary manner of an immersion heater, in liquids, or the like.

It is a further object of this invention to provide an electric resistance heater' of the constant potential type in which especially simple and effective means are employed for support-ing an insulating and heating element and electrical contacts; and a preferred embodiment of our invention may comprise simple and effective means enabling a low-potential'lamp to be advantageously used in indicating Whether'or not suitable current is actually being supplied to the coils of a comparatively high-potential heater.

It is a further object of our invention to provide a resistance heater of the general type referred to, with internal but readily adjustable automatic means for the maintenance of a' substantially constant temperature.

It is a further object of this-invention to provide an electric heater comprising comparatively simple and rugged means for attaching a flexible cord thereto; and a preferred embodiment of our invention may comprise contact elements respectively secured to inner and outer insulating plates and accessible for adjustment or repair, although the heating element of our heater is preferably permanently secured, at the factory, in the mentioned sheet metal container, in such manner that a soldered joint. or joints must beseparated before the mentioned heating element can be removed, this organization being advantageous as permitting minor repairs, although adapted to prevent tampering by unauthorized persons.

Other objects of our invention will be bctter understood from the following description of a preferred embodiment thereof, taken 1n connection with the appended claims and the accompanying drawings, in which -Fig. 1 may be regarded as a plan view, with parts broken away to a substantially median plane.

Fig. 2 is an end view, taken substantially as indicated by the arrow 2 of Fig. 1.

Fig. 3 is a transverse sectional view, taken substantially as indica-ted by the line 3-3 of Fig. 1.

Fig. 4 is a detail view, taken substantially as indicated by the arrow 4 of Fig. 1.

Fig. 5 is a. detail view corresponding to the lower right hand corner of Fig.'1 and illustrating the operation Vof a thermo-expansive element in the breaking of a circuit.

Fig. 6 is a separate view of a heating element or core of an alternative type hereinafter referred to.

Referring to the details of that specific cmbodiment of our invention chosen for purposes of illustration, 11 may be a sheet metal container, substantially rectangular in outline and preferably comparatively flat and thin, one end 12 of this container bein initially left open in order to permit the insertion of a correspondingly shaped but slightly smaller resistance heater 13 therein; and, if desired, the can or container 1l may optionally be provided with a removable cloth cover 14, shown as provided with a puckering string 15 by which it may be secured when, for instance, our heater is to be applied to the human body.

The resistance heater 13 may be formed in various Ways, one inexpensive construction comprising, as best shown in Figs. 1 and 3, a plurality of sheets of an inexpensive insulating material, such as asbestos board, a centrally disposed sheet 16 being provided with a resistance element 17, which may be a suitable length of nichrome Wire, or the like, Wound thereon, the additional sheets 18, 18', whether of the same thickness or of a lesser thickness, being employed primarily as spacing and insulating elements. As shown, the

intermediate sheet 16'of' asbestos board, or

the like, may advantageously be slightly shorter, at one or both ends, than the outer sheets 18, 18'; and filling or spacing elements 19, 19 may optionally be used in conjunction therewith, at one or both ends of the sheet 16, on which the" resistance wire. 17, vor its equivalent iswound A An important feature of our present inventionl is the method or-v organization by which we may suitably dispose and secure contact elements through which current may be delivered to the wire 17, or its equivalent. For the purpose referred to, we may employ an inner insulating plate 20,1.to which the respective ends 17 a and 17 b may be secured, as by4 means of nuts 21 andf' 21? ony screws 22 andi 22. ;f and to the inner insulating plate 20, or its equivalent, we may' also secure, as

bymeans of! screws 23,' 23 stepped'spacers- 24, 24,adapted to be retained-by-.meanssucha's'roverfl'apping straps 25, 25V and 26',k 26', whichamayl be solderedtogether,v substantially as shown at 27 in Figs. 2 and 4, in such-mannerfas-tofpreyentfV acces'sft'o the screws-23', 23', or unauthorizedf withdrawal of the described hea-tingelementiandassoci'atedparts.

Instead et'connecting'they ends of' a,V flexible cord respectively to the screws 22 andi 22, or' their? equivalents; we' consider' it preferable to1use;inc0njuncti0n withf'the men-l tioned inner?" insulating'plat'e' 20"v and the sp'acersf24,24f, or their equivalents-fan outer insulat'ii'ig4 plate 28which`y may be secured' by means suclr as readily' accessible screwsl 29; 29, andi' whichma'yi be provided with a; plur'alfit'yot' apertures, such asa pair' of smaller openings 30, 30', through which may eX- tend the' wires or al flexiblev cord", and additicn'alf apertures 312,y 31" adapted? tol receive ser'ews32f", 32,10n`e"o`r both of which-mayalso serve to retain erfengage' a Contact element extending'to or from the" binding serew- 22 or" theT binding sc'rew-y 29 .A For example, the screw 39;; mentioned; as' securing one ofi the wiresetl a exiblecord, may' be adapted di- Cil reetlly tolengagearesilient cl-ip 335, shown' as retained.'i by the" headff of thebindingl screw 22;3 andl thescrew 32 may serve incidentally to secure ai spring contactV element 342,- having aAx greater" length and'E norm ally extending llaterally into engagement with the binding screw 22', or into engagement with a contact element ietaimat thereby.V

Vlh'crr it is considered desirable lto provide "our electric: heater withI means for predeterininin-g-Vv the infaxiimi'untemperature thereof, instead? or empljyi'ngj a more complicated thermostatic' device iter this purpose we may linioyide circuit breaking meansl comprising a:-therno-expansivei element in'- the formlef a merestriaifgllit lengtlr olii suitable4 wire orv rod; andi our preferred construction ofthe element referredg to isi i-n' fact such-"that, althoughits eolefcient or expansion may lie-important to its suitability', itl is immaterialwhether' or not this elementbemetallic or' non-'metallic, cn'du'etiv'e ornoniconduct'ive.. For example,

its end, er" simply inserted' arr'outer tubular clement or pocket 36, which must have aA lesser/co-eflicient of expansion and whiclrmay be threaded?orotlie1*wise secured int-he insulating plate 20. The rod 35, being slightly longer t-han the, tubular element ,36, may normally-extend almost into contact with an intermediate portion of the spring contact. clementV 34, so that whenever the said rod is expanded by heat due to the passage oi'laxcurrent through the resistance, electrical current being normally supplied through the screw 22"to the resistance element 17 or its equivalent, asv soon;` as-a predetermined temperature is reached, the elongation of the rod' 35', or its equivalent, may be effeetiveto litt the end 37 of1 said resilient contact ele screw 38', threaded therein; andl accessible through an additional hole- 39 in the outer insulating plate 281 n lit 'being a matter of common observation that great annoyance Iis occasicned by rincer-- tainty as to whether orV not an-electrieal current is actually passing through electrical heating deviceso various sorts', we consider it advantageousto provide' oury electrical heater withindicating means such: as anin-V candescent bulb 40, shown as secured inI an additional and-f outwardly flared openingfl. and' as-vprotected by itsinterpostion between theends 30, 30 of the flexible cord 421'; and aY conductive socket 431, into which the bulb 4O1is threaded.y maybe in conductive connection with, for example, the binding screw 32 through the head of which, as described, currentmay be conducted into the resistance coil17, or its equivalent; `and in' order to ivi permitv the use of a1 low-potentialf bulb in a heater adaptedto be interposed in aI constant potential system operating at, for example,

voltsywe'v may employ means such as a short wire 44, soldered, for example; at a suitable point-in the rstturn`of the resistance wire 17, and `connected with*V aA binding screw 45, withwhich one terminal ofthe bulb-40 may make contact whenever'th'e' said' bulle` is suitably seated'L in the socket 43,01` itsequi'valent. Althoughwe may also optionally se# cure an ordinary switchy of anypreferred diesignl directlyto one of the insulatingplates 2O or28', wev consider this unnecessary, it being new possible economically' to2 provide' a flexible' cordwith interposed switch'- such I as is suggested at 46', in- Fig. 1.

The operation ofour electric heater will be fully understood frcmgthe foregoing description, in connection witlr which we 'ma-y add that the heads of the respective screws 129, 29 and the holes in which the screws 32 i tionally extend through both the steps 47 of the spacers 24, 24 and the inner insulating plate 20, are withdrawn.

Instead of providing a resistance heater of the specific character illustrated in Figs. 1 and 3, we may optionally employ a single insulating core element in the fonm of, for example, a cast glass plate, the organization illustrated in Fig. 6, for example, comprising a single plate 16', which may be formed of either a fibrous or a non-fibrous insulating material, provided with longitudinal or transverse channels 48 and with notches 49, so disposed relatively thereto that a resistance element 17 may be laced back and forth therethrough, Without liability to wear or to an accidental cont-act of any portion thereof with a metallic container or the like; and this type of heating element may optionally be provided also with a channel or pocket 36 adapted to receive a thermo-expansive elcment; and when an indicating bulb 40 is to be used in connection therewith a branch for this purpose may be taken off, for example, as suggested at 44 in Fig. 6.

Althou h we have herein.Y described a single complete embodiment of our invention and an alternative type of insulating core for our resistance heating element, it should be understood that certain features thereof might be independently used and that various modifications may be made by those skilled in the art to which this case relates without the slightest departure from the spirit and scope of our invention, as the saine is indicated above and in lthe following claims.

We claim as our invention:

l. An electric heater comprising: a substantially rectangular and flat container open at one end, a heating element comprising an insulating body supporting ak resistance extending back and forth relatively thereto; an inner insulating plate carrying inner contacts to which the ends of said resistance are secured; and means near an open end of said container for spacing said inner insulating plate therein, said spacing means being stepped and adapted to interfit with an outer insulating plate carrying outer contacts.

2. An organization as defined in claim 1 in which said inner insulating plate supports a thermo-expansive element disposed between turns of said resistance and adapted to break, at a predetermined temperature, the circuit therethrough; and in which said outer insulating plate carries an adjustable contact element adapted t0 be moved by said thermoexpansive element.

3. An organization as defined in claim l in which said spacing means are adapted to support an outer insulating plate, and in which said outer insulating plate is provided with a resilient contact element carrying an externally accessible adjusting screw engageable by a thermo-expansive element.

In testimony whereof, we have hereunto set our hands at Los Angeles, California, this 27th day of January, 1925.

EDWIN R. CROOKER. HARRY C. NEWMAN. 

